I don't do a ton of wedding cakes so here's an issue I've never thought of / encountered until now....
My wedding cake tiers are about 4"-5" tall. I've seen some taller. Just attended a wedding and the cake was lovely. But each tier was AT LEAST 8-9" tall. I thought to myself, There must be a cake plate hidden in the middle of each tier - those are really tall tiers! When time came for the wedding planner's staff to cut the cake I discovered I was wrong. It was a disaster! You just can't cut a small piece that is that tall! The top half would fall over before she got her knife all the way down to the bottom half so there was cake on the floor, on the table. The pieces didn't fit on the serving plates. It was a mess, literally, with lots of wasted cake. If I were to make tiers that tall, I'd have a separator, if even just a cardboard one just for this reason...
Any thoughts??

a good rule of thumb that I always stick to is a cake board/plate for every 4" of cake vertically. Like you said, it was a mess with a "slice" that tall. Most dessert plates won't even hold a 6" tall piece so i imagine that they had to "fold" the slice on itself to get it on the plate.

How strange. I can't imagine how it looked, either, to have all the tiers that tall. I love the look of one tall tier mixed with shorter ones, but what you're describing just sounds... odd. How many tiers was it?

When I've done extra-tall cakes, even 6" tall, when I've served them I've cut the slices a little thicker and then cut each slice in half for a serving, so it would fit on the plate. Any taller than 6" then, yes, an extra board and dowels.

The cake was 3 tiers and boy, was it tall!